In recent years, development in thin display devices such as liquid crystal display devices and organic EL display devices has been rapidly advanced. In many cases, these thin display devices include active matrix substrates on which switching elements each configured to drive associated one of a plurality of pixels are provided to the pixels in order to enhance display quality.
That is, a display device includes the active matrix substrate as described above and a counter substrate disposed to face the active matrix substrate and bonded to the active matrix substrate via a frame-like sealing member. The display device has a display region surrounded by the sealing member and a non-display region around the outer periphery of the display region.
In a region of the active matrix substrate which will serve as the display region, for example, thin film transistors (TFTs) serving as switching elements are each provided to an associated one of a plurality of pixels. The TFTs include a semiconductor layer made of, for example, amorphous silicon (a-Si). Moreover, each pixel includes a pixel electrode connected to the TFT.
On the other hand, in a region of the active matrix substrate which will serve as the non-display region, a plurality of terminals are formed outside the sealing member. External circuits are connected to the plurality of terminals. Moreover, each terminal is formed at an end portion of a lead line extended from the display region.
FIG. 59 is an enlarged cross-sectional view illustrating a vicinity of a sealing member of a conventional display device. As illustrated in FIG. 59, a sealing member 103 is disposed between an active matrix substrate 101 and a counter substrate 102. On the active matrix substrate 101, a lead line 104 is formed in a formation region for the sealing member 103. The lead line 104 is covered with a gate insulating film 105 and a protection film 106 so that the lead line 104 is protected. Moreover, an interlayer insulating film 107 made of a photosensitive organic insulating film is formed on the gate insulating film 105 and the protection film 106. Although not shown, the interlayer insulating film 107 is also formed in the display region. On a surface of the interlayer insulating film 107 in the display region, pixel electrodes are formed. On the other hand, in the formation region for the sealing member 103, the sealing member 103 is formed on the surface of the interlayer insulating film 107.
Here, when an active matrix substrate including a plurality of a-Si TFTs formed thereon is fabricated, for example, a process using five masks is known. In the process using five masks, a gate material layer is patterned by using a first mask, and an a-Si layer is patterned by using a second mask. Further, a source material layer is patterned by using a third mask, and a photosensitive organic insulating film is patterned by using a fourth mask. By using the photosensitive organic insulating film as a mask, an insulating film such as a gate insulating film is etched. Then, an indium tin oxide (ITO) film which will serve as a pixel electrode is patterned by using a fifth mask.
Thus, in the formation region for the sealing member, in order to form the gate insulating film and the protection film which protect the lead line, an interlayer insulating film made of the photosensitive organic insulating film has to be left on the gate insulating film and the protection film.
However, in the display device described above, outside moisture permeates via an interface between the sealing member and the interlayer insulating film into a region surrounded by the sealing member (i.e., toward the display region), which leads to a problem where display quality is impaired, thereby reducing display reliability.
To address this problem, Patent Document 1 discloses that in the formation region for the sealing member, a groove is formed in the interlayer insulating film, and the sealing member is formed in the groove and on a surface of the interlayer insulating film at both sides of the groove. This configuration aims to prevent the permeation of moisture via the interface between the sealing member and the interlayer insulating film.